Intracrine oestrogen production and action in breast cancer: An epigenetic focus

► Oestrogen biosynthesis enzymes, such as aromatase, are regulated by epigenetics. ► Epigenetic status is important in progression of oestrogen dependent tumours. ► Oestradiol (E2) is a potent modulator of epigenetic modifying enzymes. ► Endocrine resistance is a process that can be attributed to epigenetic changes. ► HDAC inhibitors are a novel treatment against endocrine resistant breast cancers.